I suggest you put a plate between the egr valve and the intake manifold as well as pluging the vac line. plug the vac line up close to the control valve (on the valve cover) the egr valve has a tendencie to leak vacuum. put a plate under the egr valve, mine was frozen in the partally open position, pluging the vac line would not have stopped exahust gasses from going in the intake manifold. I used a small piece of stainless I had lying around. use an egr valve gasket as a template. WD40 is recommended on the egr valve attach bolt as they can get pretty rusted up. you dont' want to break them off. I had the intake manifold cleaned before I did this, it's still pretty clean inside after 20k miles. you could pull the whole system off, but that might be noticed if you have emissions testing done in your area like we do in Denver.

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Kevin
82 300D